Pilger rolling process and roll for performing same



Sept. 13, 1932. L. KLE IN 1,876,691

PILGER ROLLING PROCESS AND ROLL FOR PERFORMING SAME Filed March 24, 1950 Patented Sept. 13, 1932 LUDWIG KLEIN, OF DUSSELDORF, GERMANY TPILGER ROLLING PROCESS AND ROLL FOR PERFORMING SAME Application filed March 24, 1930, Serial No. 438,600, and in Germany April 2, 1929.

is surfaced. It has now been found, that the process, if performed in this manner with accordingly calibrated rolls, exerts a detrimental influence on the stretching of the material. The cause of this is that toward the end of the stretching procedure the depth of the pass between the rolls is steadily reduced, whereby the tube material is backed up so much that the rolls are not able to forge it continuously. It is therefore impracticable to reduce the wall thickness of the finished tube to the extent required for a marketable product.

The backing up and accumulation of the material causes so high a pressure between the rolls and the mandrel, that the tube metal is distorted and the rolls and the mandrel are subjected to excessive wear. The distortion and overstressing of the metal may become 'so heavy that cracks may formin the tube.

According to my invention these drawbacks are eliminated and the weight of the tube per unit of length is reduced to the extent required by practical considerations, which could not be obtained heretofore by the pilger process. i

This improvement is effected 'by subdividing the rolling process into several'alternating stretching and surfacing stages. In this manner each stretching pass is supplied only with the amount of material which it is able to forge without excessive pressure and stress. 7 o

Preferably the stretehin passes are so arranged that in each succeeding pass the wall thiclmess is reduced to a greater extent, than in the next preceding stretching pass. In

this manner thin-walled tubes are obtained, without unduly increasing the wear of the rolls and mandrcls and without overstraining the tube metal.

It has been found that by subdividing the process as described it is possible to obtain wall thicknesses which are 30% less than the smallest thiclmesses which could heretofore be obtained by the pilger process.

In the drawing aflixed to this specification 60 and forming part thereof a pilger roll having two stretching and two surfacing passes is illustrated diagrammatically by -way of example, together with the tube obtained by the processv 6 In the drawing Fig, 1 is a cross section of the roll, and

Fig. 2 is an axial section showing part of the tube. A

Referring now to the drawing, 1, is a roll and 2 is its central portion in which the passes are formed. a and 0 are eccentric passes for stretching the tube, and b and d are centric surfacing passes. Preferably the eccentricity of the first stretching pass a is greater than that of the second stretching pass 0. If v a third stretching pass is provided, its eccentricity should be smaller than that of the pass a, and so on.

As shown in Fig. 2, the wall thickness 8 imparted to the tube 3 in the first stretching pass a remains constant in the first surfacing pass 6 and is then reduced in the second stretching pass a to the final thickness 8' which is preserved during the second surfacing stage (1.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

In the claims affixed to this specification no selection of any particular modification of the invention is intended to the exclusion of othermodifications thereof and the right to subsequently make, claim to any modification not covered by these-claims is. expressly reserved.

I claim:

1. A pilger tube rolling process in which each bite of the rolls results in a plurality of alternating stretching and surfacing operations.

2. A pilger tube rolling process subdivided into a plurality of alternating stretching and surfacing stages, in which the tube metal is stretched less in the second stretching stage than in the first stretching stage.

3. A pilger roll comprising two eccentric passes and a centric surfacing pass between said straight passes.

4. A pilger roll comprising two eccentric stretching passes and a centric surfacing pass between said eccentric passes, the eccentricity of the first stretching pass being greater than that of the second stretchin pass.

In testimony whereof I a x my signature.

LUDWIG KLEIN. 

